Marin County health officials are investigating a potential E. coli outbreak after the bacterial infection was detected in three children and is suspected in an adult.

Three people sickened live in Tiburon; a fourth lives in Inverness. No definitive source for the bacteria has been identified, but health officials believe the residents were exposed to the bacteria between Sept. 11 and Sept. 15. There have been no new documented cases since the initial outbreak.

Dr. Matthew Willis, Marin County public health officer, said E. coli infections are most serious in children, elderly people and those with weak immune systems.

"Three of the four cases are children and two of them have been hospitalized, but are in stable condition," Willis said.

He said Marin public health authorities are working with the California Department of Public Health to gather information from clinicians and patients to determine whether the cases are linked to each other or possibly to out-of-state cases.

"We contact the patients themselves to interview them about their food history. We try to determine where they've eaten and what they've eaten to see if there's a common source," Willis said.

An E. coli infection usually occurs after people eat food containing the bacteria, such as unpasteurized dairy products or undercooked meat, according to the Centers for Disease Control and Prevention.

Residents are reminded to follow good food hygiene practices, including washing hands with soap and water after changing diapers and using the bathroom, and before preparing or eating food. Meats should be cooked thoroughly and counters, cutting boards and utensils washed after touching raw meat.

The bacteria's incubation period is about three to four days after exposure, but can be as short as one day and as long as 10 days. Willis said the four people currently affected by the bacteria began having symptoms between Sept. 16 and Sept. 18.

Symptoms of an E. coli infection include severe stomach cramps, diarrhea, bloody diarrhea and vomiting. Anyone experiencing these symptoms is encouraged to visit their doctor.